Manufacture of articles from synthetic resin compounds



E. MHRING Filed March 16, 1932 2 Sheets-Sheet 1 May 22, 1934.

MANUFAGTURE oF ARTICLES FROM SYNTHETIC RESIN coMPoUNns 3. .ma F

E. MHRING 1,960,120 MANUFACTURE OF ARTICLES FROM SYNTHETIC RESIN COMPOUNDS May 22, 1934.

Filed March 16. 1952 2 Sheets-Sheet 2 inve/Tan BY.' 1 yf Patented May 22, 1934 MANUFACTURE 0F ARTICLS FROM 'SYN- THETIC RESIN COMPOUNDS Erich Mhring,

Moosbierbaum Heiligenech,

Austria, assignor'to the firm Saureschutz Gesellschaft m. b. H., Berlin-Altglienicke, Germany Application March 16,

1932, Serial No. 599,293

In Austria March 23, 1931 'l Claims.

This invention relates to the manufacture of articles from synthetic resin compounds, and has for its object to simplify and cheapen the manuacturing process, and more particularly the hardening stage of `this process. Synthetic resin compounds are subjected, in the hardening and 'nishingstage of the manufacturing process, to the action of heat by means of hot presses, autoclaves, drying kilns, and the like.

In accordance with the present invention the hardening is carriedout by means of heatgenerated in electric resistances disposed in on or about the compound to be hardened. This method enables articles of any size to be manufactured wherever required, since the manufacturing process is rendered independent of presses, autoclaves, or furnaces. Further, the cost of the forms of moulds required in the hot pressing process is avoided.

The progress of the hardening and drying process can be regulated as desired. A particular advantage of the new process is that the Water liberated is removed or driven oi without the formation or" bubbles. since the heating can be made to proceed from the interior towards the outside of the articles orpiece being hardened. In this manner the subsequent ageing of the product, and more particularly the formation of cracks, is eliminated. If the blocks or articles to be hardened are of such cross-section or of such dimensions that a plurality of resistance Wires are arranged adjacent to each other or one above the other, it is advisable to connect these wires in a number of circuits so that the progress of the hardening can be regulated as desired, and can be made to proceed, for instance, from the middle of the piece to be hardened gradually towards the outside or the same.

According to the present process huid synthetic resin compounds, which are manufactured with an acid or alkaline catalyzer or according to any other known method, and which are mixed with asbestos, wood, cotton, paper, or any other filling 4 materials used, are pressed or poured into moulds in a manner similar to that usual in concrete Work, a suitable metallic conductor being at the same time embedded in the material. Non-filled synthetic resin of suitable composition and properties can also be employed.

If it is desired to manufacture a box or a tube, for example, the procedure is as follows:'-A core of wood or metal is first made and then covered with a layer of say 10 millimetres of synthetic resin mixture. Resistance wire is then wound about the Wholeat intervals of, for example, 10

(Cl. Iii-59) mm. A further layer of filled synthetic resin mixture is then again applied. As a precaution the outer layer may be covered; ii desired, with Wood, or equally well with linen or paper, so as to keep the synthetic resin mixture in place and to prevent the same from shifting. The ends of the resistance Wires are then connected to a source of' current which is then so regulated that the wires are heated to a temperature of 50-80 degrees centigrade. After some 12-24 hours, according to the temperature ofx the wires and the nature of the resin compound, this latter becomes hard. With the employment or acid resins the hardening is generally more rapid than with alkaline resins. When once the composition is hard the enveloping covering or form can be removed. The article is-then finished, although it Vis in practice advisable to continue heating the article for some time after the removal or the covering or form. with the aid or the resistance wires, in order that all trace of Water may be driven off. It is possible in this manner to manufacture large receptacles as used in the chemical industry withouta press or any other of the devices usually employed in the hardening of synthetic resin, and to manufacture the same wherever required. It is equally possible to manufacture tubes, plates, and blocks of any desired size by this method. It is also perfectly possible to vuse this method 'for making seamless roof coverings, road surfaces, and floor coverings, wall coverings, and the like.

In the case of articles of comparatively slight cross-section the electric resistance can be adapted to the shape or contour of the outer surface of the articles to be finished, care being taken to ensure that the same can be removed after use. A particularly simple method is thusprovided for producing objects of any desired size and shape. The laying or insertion of the individual resistance wires for the manufacturing of each single article can bc avoided ii. the compound, after havingbeen rammed into or packed about a form, be covered over with suitably shaped heating resistances, for example plates of insulating material which are covered or wound in a known manner with heating'wires. The simplest possible carrying out of the method or manufacturing synthetic resin bodies provided by the present invention consists in the employment of one or more forms whichv are themselves carriers of a supercially disposed resistance wire. lt is also possible to arrange for the subsequent removal of heating Wires embedded in the compound, after lll@ completion or the hardening process, provided these wires be straight.

Already hardened parts made of synthetic resin can alsobe connected together in accordance with the present method by the interposition of unhardened synthetic resin compounds, and it is particularly advantageous in this connection that, for the purpose of hardening the intermediate layer of slight dimensions, it is not necessary at the same time to heat the entire remaining synthetic resin compound.

In the manufacturing of larger articles it is advisable to mix the raw materials consisting of filling substances and the components of the synthetic resin together with the catalyzer in situ, and to start the reaction with the aid of the electric resistances incorporated therein, so that the compound is converted into the finished state in one unbroken process.

In certain cases the inserted wire can bearranged to full a separate purpose, independently of the hardening, as for instance that of reinforcementfor increasing the strength of the nished product, as in the reinforcement of concrete, more particularly when the finished articles are intended for use as a building material.

Synthetic resin is to be taken to include for the purpose of the present invention phenolic articial resins, phthalic acid glycerine, urea-formaldehyde, and similar condensation products. For the purpose of the electric resistance any suitable material can be used, more particularly nickelin, constantan, iron, and the like. The same c an be used in the form of wire, strip, netting, or in any other desired form. Metallic powder in suitable quantities and distribution can also be introduced into the synthetic resin compound in such a manner that it becomes a conductor of the electric current. The strength and density of the resistance employed will vary according to the nature of the synthetic resin used.

In the drawings the invention is illustrated in several examples. Fig. 1 shows the manufacturing of a tube; Fig. 2 the manufacturing of a great acid-proof cistern, Fig. 3 being a wiring plan of the resistance wires thereby used, and Fig. '4 a view of one edge of the cistern, showing the fastening of the resistances to the sheetings which are partially broken away; Figs. 5 and 6 show the application of an elbow to the Wall of a cistern; and Fig. 7 shows the manufacturing of a small cup.

In Fig. 1,A 1 denotes a cylindrical woodor metal-core with a thickened end 2. Upon said core there is laid on a layer 3 of unhardened synthetic resin and a resistance wire of nickelin or constanten is wound around said layer. 'I'hen follows an external synthetic resin layer 5, which is rmly wrapped by means of a cloth strip 6. The ends 7 of the wire winding 3 are brought out and connected to a source of electric current. As already mentioned, the heating temperature shall amount to about 50-80 degrees centigrade and the duration of heating to 12-24 hours'. Thereafter core 1 and wrapping 6 are removed, the heating of the freed tube is however continued for some time in order to drive off all traces of water.

Fig. 2 illustrates the manufacturing 'of a rectangular acid-proof cistern. Previously such vessels could not be manufactured in one piece but to certain dimensions, greater pieces were composed from .several parts or were provided with an acid-proof lining only. In accordance with this invention the cistern is manufactured on its iinal standing place and may therefore take even the greatest dimensions without diiculty. Upon a convenient base 8, for instance a concrete socket, there is at first erected an external falsework 9. As electric resistances there are used zigzag laid wires 10 knotted together with non-conducting cords 1l of hemp or the like, so as to form net works 13. In the drawings there is assumed for the sake of simplicity that the basis is about twice as broad as the cistern is high, so that the said net works are enabled to be employed in a unique breadth.

Three pairs of adjacent nets are spread in equal distances parallel to the base 8 by iixing the ends of the cords 1l to the Walls of the falsework by the intermediary of nails 12, In order to obtain also along the longitudinal edges of the net several supporting points, cords 14 are preferably interlaced in the nets and their ends nailed to the falsework.

Further threenets are spread vertically in a rectangle parallel to the walls of the falsework by fastening the nets in the edges to the falsework by the intermediary of cords l1', respectively in the one edge where the nets begin and terminate by the intermediary of their own cords 1l (cf. also Fig. 4).

The wires of corresponding horizontal and vertical nets 13, in the drawings denoted from the interior of the cistern to its outside by the indices I-III, are connected in accordance with the wiring diagram of Fig. 3 in series and over a regulator Rr-m to the electric current network.

These preparatory steps being finished the base of the mould is ll'ed up with unhardened synthetic resin up to a level corresponding to the thickness of the ground Wall of the cistern. It is understood that this wall may also be cast up in four layers mounting and fastening the net works 13m, 1311, 131 between each two layers. After the bottom plate is cast up, an internal falsework 15 is erected and the thus formed mould for the vertical cistern walls illled up with an equal unhardened synthetic resin com- 3 pound. Now by operating the regulators R current is sent through the wires 10 the middle circuit II being cut in at iirst, while the circuits I and III are connected to the source of current at a somewhat latertirne. The heating is continued after the removal of the falsework in order to drive 01T all remainders of water.

If now for instance an elbow 16 as it is delivered in nished state is to be applied to a Wall of the cistern there will be proceeded in accordance with Figs. 5 and 6:--Around the perforated or hollowed out opening 17 in the vcisten wall 18 there is sunk in a recess 19, a

layer 20 unhardened synthetic resin filled therein, a wirewinding 2l laid thereupon and a second synthetic resin layer plastered thereover, to which the ilange of the elbow of hardened synthetic resin is applied, convenient means being provided for holding said elbow in position. If the interposed layers 20 and 22 are now hardened by sending an electric current through the winding 22, there is obtained a tight and durable connection of the cistern wall with the elbow.

For manufacturing a small cup 23 in accordance with Fig. '7 there is employed a smooth plunge die 24 and a female die 25 of refractory cl y or the like which on its inner surface /is provided with a resistance winding 26. A cup formed previously is set upon the plunger die, the female die is tilted over the cup and the electric current is cut in. After the compound is hardened the female die is removed and the completed cup taken away from the plunger die.

If the plunger and the female die are to be employed directly for the forming of the cup and a smooth external surface of the latter is required, the female die is lined with a layer 27 of a wax the melting point of which lies above the hardening temperature. A smooth surface may preferably also be obtained by providing the refractory clay die with a lining of graphite instead of Wire windings as electric resistance.

l. The method of making articles from synthetic resinous compounds which comprises forming the article to the final-desired shape from a synthetic resinous compound in its unhardened condition and providing electric resistance in direct contact therewith; passing electric current through said resistance; and converting the synthetic resin to its nal hardened condition and removing substantially all the water therefrom under atmospheric pressure by the heat generated in said resistance.

2. The method of making articles from synthetic resinous compounds which comprises forming the article to the final desired shape from a synthetic resinous compound in its unhardened condition with electric resistance embedded therein; passing electric current through said resistance; and converting the synthetic resin to its nal hardened condition and removing substantially all the water therefrom under atmospheric pressure by the heat generated in said resistance.

3. The method of making articles from synthetic resinous compounds which comprises forming the article to thenal desired shape from a synthetic resinous compound in its unhardened condition with electric resistance embedded therein, said resistance being placed with relation to the resin so that subsequent hardening will proceed from the interior outwardly; passing electric current through said resistance; and converting the synthetic resin to its nal hardened condition and removing substantially all the water therefrom under atmospheric pressure by the heat generated in said resistance.

4. The method of making articles from 'synthetic resinous compounds which comprises forming the article to the final desired shape from a synthetic resinous compound in its unhardened condition with electric resistance embedded therein, said resistance being divided into a plurality of independent current circuits arranged successively in the interior of the article; passing electric'current through said circuits in a manner to harden the synthetic resinous compound progressively from the interior to the surface of the article; and converting the synthetic resin to its final hardened condition and removing substantially all the water therefrom under atmospheric pressure by the heat generated in said resistance.

5. The method of making articles from synthetic resinous compounds which comprises placing the synthetic resin components together with a catalyst and filling material in a mold with electric resistance embedded in said mixture of materials; passing electric current through said resistance; and converting the synthetic resin to its nal hardened condition and removing substantially al1 the water therefrom under atmospheric pressure by the heat generated in said resistance.

6. The method of making articles from synthetic resinous compounds which comprises placing between two hardened synthetic resinous products a synthetic resinous compound in its unhardened condition in its nal desired shape and providing electric resistance in direct contact with said unhardened resin; passing electric current through said resistance; and converting the synthetic resin to its final hardened condition and removing substantially all the water therefrom under atmospheric pressure by the heat generated in said resistance.

'7. The method of making articles from synthetic resinous compounds which comprises placing between two hardened synthetic resinous products a synthetic resinous compound in its unhardened condition in its final desired shape with electric resistance embedded in said unhardened resin; passing electric current through said resistance; and converting the synthetic resin to its final hardened condition and removing substantially all the water therefrom under atmospheric pressure by the heat generated in said resistance.

ERICH MHRING. 

